"This is our mother and her health is paramount. We are not inventing or plotting anything. We are following doctor's advice. Period," he added.

Paris Jackson's responded to her uncle's claim with her own tweet early Sunday. "the same doctor that testified on behalf of dr murray saying my father was a drug addict (a lie) is caring for my grandmother... just saying" she tweeted.

Dr. Metzger was brought into Jackson's Calabasas, California, home "under false pretenses" by saying he was sent by her primary care physician, Ribera said. "We came to find out that her doctor has no association with Dr. Metzger."

The doctor advised Jackson that it was better for her to take a plane on a trip planned for the next day, rather than ride in a RV driven by Trent Jackson, Ribera said.

Jackson left with her oldest daughter, Rebbie, the next day to fly to Albuquerque, New Mexico, to attend a Jackson brothers concert two days later, she said. But she never arrived at the concert, Ribera said.

When Paris Jackson called her aunts Rebbie and Janet over the past several days to find her grandmother, she was told each time she could not speak to her, Ribera said.

In another tweet, Paris Jackson gave out her bodyguard's phone number and asked people to call the authorities if they saw her grandmother.

"The kids were trying to get a hold of their grandmother and they haven't been able to reach her for almost a week," Ribera said. "They are told she's unavailable."

"I'm concerned that she's not safe," Ribera added.

Jackson "has never gone 24 hours without talking to her kids," she said. "I'm concerned that she would never do this. We have no idea what's going on with her. No one has talked to her."

CNN reached out to Janet Jackson's representatives several times but did not hear back.

The sheriff's homicide-missing persons unit has been asked to investigate, Ribera said.

A letter was made public Wednesday in which two daughters, Rebbie and Janet, and three sons -- Jermaine, Randy and Tito -- charge that Katherine Jackson was being mistreated by the executors of Michael Jackson's estate and mis-advised by her manager and lawyer.